What size air conditioner do I need for my home?

As with most questions...it depends. To properly size your air conditioner, a general rule-of-thumb is as follows:

1. Southern Half of the United States: use one-ton of cooling power for every 400 square feet of your house. So, for a 2,000 sq/ft. house, you'd likely need a 5-ton air conditioner.

2. Northern United States & Canada: use one-ton of cooling power for every 500 square feet of your home. So, in Montana, for instance, a 2,000 sq/ft. house would likely need a 4-ton air conditioner.

These are just general rules, however, and don't account for other air conditioner sizing variables, such as the R-value of your insulation, sun exposure, ceiling height, etc. To get a more accurate size for your air conditioner or furnace, try ASM's HVAC Design and Consultation Program.